Automatic fire protection sprinklers generally include a body with a base, an inlet defined by the base and connectable to a source of fire retardant fluid under pressure, an outlet defined by the base, a passageway between the inlet and outlet, a flow-controlling orifice located generally just upstream of the outlet, a cap closing or sealing the outlet when the sprinkler is in its normal or standby state, a thermally sensitive mechanism which breaks apart and releases the sprinkler into its operating state when its temperature is elevated to within a pre-determined range, thereby allowing the pressurized fluid to move the cap away from its closed position and discharge from the outlet, and a deflector supported by arms or pins that extend from the base, in the sprinkler operating state, the deflector being positioned opposite the outlet for distribution of the fire protection fluid over a pre-selected region to be protected by the sprinkler from fire. Fire retardant fluid may include natural (potable) water, natural seawater, or selected mixtures of one or more additives with either type of water to enhance the fire fighting properties of the fire protection system. The cap may be separate from the deflector, may be separable from the deflector upon operation of the sprinkler, or may be fixed to the deflector. In one type of sprinkler, the deflector may be secured to arms that extend from the body to hold the deflector in a fixed position that is the same for both standby and operating states. In another embodiment, the arms or pins may be slidable within guide holes in the base portion, the deflector thereby being caused to move away from the outlet into its operating position upon release of the thermally sensitive mechanism.
Thermally sensitive release mechanisms, including those suitable for use in this invention, consist of a thermally sensitive element (e.g., a frangible bulb) which breaks apart when its temperature is elevated to within a prescribed operating temperature range, such as by heat from a fire, and a linkage mechanism that holds the cap closed when the sprinkler is in standby or closed condition, due to the interconnection between the cap and the thermally sensitive element. The cap is released upon breaking apart of the thermally sensitive element, and the fire protection fluid rushes from the outlet (e.g., initially downward for pendent-type fire sprinklers and initially horizontally for horizontal sidewall-type fire sprinklers). In the case of a pendent-type fire sprinkler, the fire protection fluid impacting the deflector is distributed downward and outward in a generally hemispherical pattern over the specified area to be protected from fire. In the case of a horizontal sidewall-type fire sprinkler, the fire protection fluid impacting the deflector is distributed downward and outward in a generally quarter-spherical pattern over the specified area to be protected from fire. The exact shape of the spray pattern for either type of sprinkler is, in large part, a function of the deflector configuration. However, in both cases, the character of the spray pattern can also be affected by any portion of the fire protection fluid impacting the deflector support arms or pins, either directly or after first striking the deflector. The character of the spray pattern can also be altered by any portion of the fire protection fluid impacting the cap, if it is fixed to the deflector and not thrown free upon operation of the sprinkler.
In addition to mounting orientation, a sprinkler is also categorized by the type of occupancy for which it is designed. Examples include: residential, commercial (e.g., mercantile), warehousing, and institutional, such as for correctional, detention, and mental health care facilities. So-called institutional sprinklers, e.g., including of this invention, have additional design requirements beyond those associated with conventional sprinklers used, e.g., in commercial and residential occupancies. For example, institutional sprinklers have a thermally sensitive release mechanism designed to be tamper resistant and to help reduce the opportunity for occupants to injure themselves or others, e.g., with components of the mechanism that might be broken away by tampering. In addition, it is an industry-accepted general design criteria that, in the standby state, in order to help prevent suicide, the thermally sensitive release mechanism should break away from the body of the sprinkler when a hanging load of 75 pounds or more is applied, e.g., by a cord, wire or the like.
In recent years, in situations where safety is a primary consideration in the selection of a fire protection sprinkler system for a particular occupancy, the use of quick response-type sprinklers has been increasingly specified. This is particularly true in the case of institutional occupancies, and the trend has been supported by revisions incorporated into the 1996 edition of the National Fire Protection Association's "Standard for Installation of Sprinkler Systems" ("NFPA 13"). The 1996 edition of NFPA 13 specifies that sprinklers in "Light Hazard" classification occupancies shall be of the quick response-type, and it also specifies that institutional occupancies are considered to fall within the "Light Hazard" classification. The need for quick response-type sprinklers in institutional occupancies has represented a particular challenge to sprinkler manufacturers. This is because the thermally sensitive elements in quick response-type sprinklers are generally more fragile, e.g. than those in standard response-type sprinklers, due, e.g., to the relatively smaller size and mass necessary to meet the rapidity of operation requirements of quick response-type sprinklers. However, as the surrounding structure provided to protect the thermally responsive element of an institutional sprinkler is increased, e.g., to better resist tampering, the restriction to flow of heated gases from a fire around the thermally responsive element, e.g. as necessary to raise its temperature to actuate the sprinkler, is generally increased, thereby hindering the rapidity of operation.
The use of frangible bulbs as thermally sensitive elements in automatic fire protection sprinklers has long been established. However, up until now, frangible glass bulbs in automatic fire protection sprinklers have been employed exclusively with application of opposing axial compression loads near their axial ends (commonly referred to as the "spherical" and "stem" or "pip" ends). Tramm U.S. Pat. No. 5,810,263 shows an example of an automatic fire protection sprinkler in which the frangible glass bulb is axially loaded between a compression screw engaging the spherical end of the bulb and a cap engaging the stem end of the bulb. Examples of automatic fire sprinklers with the frangible glass bulb axially loaded proximate to the spherical and stem ends, e.g. by a linkage mechanism holding the cap closed, are seen in Klein U.S. Pat. No. 4,800,961; Barnett et al. U.S. Pat. No. 4,930,578; Polan U.S. Pat. No. 4,976,320 and U.S. Pat. No. 5,083,616; Eynon U.S. Pat. No. 5,234,059; and Hoening et al. U.S. Pat. No. 5,299,645.